The present invention relates to telephony, and in particular to an audio conferencing platform.
Audio conferencing platforms are well known. For example, see U.S. Pat. Nos. 5,483,588 and 5,495,522. Audio conferencing platforms allow conference participants to easily schedule and conduct audio conferences with a large number of users. In addition, audio conference platforms are generally capable of simultaneously supporting many conferences.
Due to the widespread popularity of the World Wide Web, Internet traffic is at an all time high and rapidly increasing. In addition, the move towards IP communications is gathering momentum. Users are currently using the Internet as a mechanism for retrieving streamed audio and video media streams.
There is a need for an audio conferencing system that can stream its summed conference audio onto the Internet in real-time. This will allow a user to listen to an audio conference supported by the audio conferencing system, over the Internet.
Briefly, according to the present invention, an audio conferencing system comprises an audio conference mixer that receives digitized audio signals and sums a plurality of the digitized audio signals containing speech to provide a summed conference signal. A transcoder receives and transcodes the summed conference signal to provide a transcoded summed signal that is streamed onto the Internet.
In one embodiment an audio conferencing platform includes a data bus, a controller, and an interface circuit that receives audio signals from a plurality of conference participants and provides digitized audio signals in assigned time slots over the data bus. The audio conferencing platform also includes a plurality of digital signal processors (DSPs) adapted to communicate on the TDM bus with the interface circuit. At least one of the DSPs sums a plurality of the digitized audio signals associated with conference participants who are speaking to provide a summed conference signal. This DSP provides the summed conference signal to at least one of the other plurality of DSPs, which removes the digitized audio signal associated with a speaker whose voice is included in the summed conference signal, thus providing a customized conference audio signal to each of the speakers.
In a preferred embodiment, the audio conferencing platform configures at least one of the DSPs as a centralized audio mixer and at least another one of the DSPs as an audio processor. Significantly, the centralized audio mixer performs the step of summing a plurality of the digitized audio signals associated with conference participants who are speaking, to provide the summed conference signal. The centralized audio mixer provides the summed conference signal to the audio processor(s) for post processing and routing to the conference participants. The post processing includes removing the audio associated with a speaker from the conference signal to be sent to the speaker. For example, if there are forty conference participants and three of the participants are speaking, then the summed conference signal will include the audio from the three speakers. The summed conference signal is made available on the data bus to the thirty-seven non-speaking conference participants. However, the three speakers each receive an audio signal that is equal to the summed conference signal less the digitized audio signal associated with the speaker. Removing the speaker""s voice from the audio he hears reduces echoes.
The centralized audio mixer also receives DTMF detect bits indicative of the digitized audio signals that include a DTMF tone. The DTMF detect bits may be provided by another of the DSPs that is programmed to detect DTMF tones. If the digitized audio signal is associated with a speaker, but the digitized audio signal includes a DTMF tone, the centralized conference mixer will not include the digitized audio signal in the summed conference signal while that DTMF detect bit signal is active. This ensures conference participants do not hear annoying DTMF tones in the conference audio. When the DTMF tone is no longer present in the digitized audio signal, the centralized conference mixer may include the audio signal in the summed conference signal.
The audio conference platform is capable of supporting a number of simultaneous conferences (e.g., 384). As a result, the audio conference mixer provides a summed conference signal for each of the conferences.
Each of the digitized audio signals may be preprocessed. The preprocessing steps include decompressing the signal (e.g., xcexc-Law or A-Law compression), and determining if the magnitude of the decompressed audio signal is greater than a detection threshold. If it is, then a speech bit associated with the digitized audio signal is set. Otherwise, the speech bit is cleared.